1. Field of the Invention
The present invention relates in general to a solid-state imaging device and, more particularly, to a solid-state image sensor having photosensitivity or being photosensitive to a plurality of different wavelength ranges such as visible light and infrared light wavelength ranges.
2. Discussion of Background
Although developed largely for military purposes, infrared imaging devices have been important in industrial, commercial, and scientific applications. For example, infrared imaging systems, which include a solid-state infrared image sensor, where developed to achieve a nighttime aerial photographic capacity.
As generally known, a solid-state imaging device comprises photosensing cells which are arranged in a matrix form on a semiconductor substrate. When a plurality of irradiation light components respectively having different wavelength ranges (e.g., visible light and infrared light) is detected using a solid-state imaging device such as a charge-coupled device (to be referred to as a "CCD" hereinafter), CCDs for visible light and infrared light wavelength ranges are used. In this case, there is prepared, an image sensor chip in which a photosensing cell for visible light and a photosensing cell for infrared light are formed to be adjacent.
However, in solid-state imaging devices of this type, since photosensing sections independently sensing light components of different wavelength ranges are formed adjacently on a single substrate, the pixel density as input light of one wavelength range becomes undesirably halved. In other words, high-density images cannot be obtained at the same time as input light containing two different wavelength ranges.